The arrangement of metamorphic rocks into types according to the deformation they experienced, in particular whether or not they exhibit foliation, indicating whether they were subjected to directed pressure or shear stress, although some do not exhibit foliation because their minerals do not show alignment. Rocks are also classified by metamorphic grade as very low, low, medium, and high. The table shows a selection of parent rocks and the changes effected by metamorphism.
Parent rock | Very low grade 150–300 °C | Low grade 300–450 °C | Medium grade 450–550 °C | High grade Above 500 °C |
|---|
Mudrock | Slate | Phyllite | Schist | Gneiss |
Granite | No change | No change | No change | Granite gneiss |
Basalt | Chlorite schist | Chlorite schist | Amphibolite | Amphibolite |
Sandstone | No change | Little change | Quartzite | Quartzite |
Limestone | Little change | Marble | Marble | Marble |
https://opentextbc.ca/geology/chapter/7-2-classification-of-metamorphic-rocks/ Classification of Metamorphic Rocks.